Acronym · Packaging & Assembly
QFN (Quad Flat No-lead)
A small leadframe package with perimeter pads on the underside and no protruding leads, usually with a large exposed thermal pad in the centre. It gives low inductance and good thermal performance in a very small footprint.
- Also known as
- MLF, MLP, Micro Leadframe Package
- Type
- Acronym
- Domain
- Packaging & Assembly, Package families
Notes
Ubiquitous in power management, RF and sensor parts; inspection is harder because the joints sit under the body.
Overview
A QFN (quad flat no-lead) package is a small plastic package built on a copper leadframe, with flat contact lands around the edge of its underside instead of leads sticking out of its sides, and usually a large exposed metal pad in the centre. It is soldered directly onto the circuit board, which keeps it close to the size of the die and gives short, low-inductance connections. QFNs are widely used where size, weight and performance matter, such as in phones and tablets, and the family goes by many names, including MLF, VQFN, LFCSP and, for two-sided versions, DFN or SON.
How it works
The die is attached to the central paddle of a copper leadframe and wire bonded to the surrounding leads, and the whole strip is encapsulated in mould compound. The leads and the paddle are left exposed on the bottom face. Packages are then separated either by sawing through a moulded array, the saw format, or by punching individually moulded units out of the frame, the punch format.
The exposed die paddle is the key thermal feature: soldered to a copper area on the board, it gives heat a short path out of the chip, and it can also act as a ground connection through down bonds or conductive die attach. Because the leads are short and flat, their parasitics are small; Amkor's datasheet lists lead inductances of about 0.5 to 2.2 nH depending on package size and lead position. Amkor offers body sizes of about 1 to 13 mm and up to 180 connections in dual-row versions.
The main drawback is that the solder joints sit under the package, where they are hard to see. Automotive customers require solder fillets that automated optical inspection can check, so wettable flank designs, such as a dimple etched into the end of each lead, make solder climb the package edge.
Related terms
Part of the Packaging & Assembly glossary, with every term in the topic and the lifecycles, tools and standards that use them.
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